Meanwhile in a 4- to 6-quart Dutch oven cook the spinach in lightly salted boiling water, half at a time, for 1 minute or until wilted. Drain and cool slightly; squeeze out excess liquid. Coarsely chop the spinach; set aside. In a medium saucepan combine half-and-half and cornstarch; cook and stir until thickened and bubbly. Stir in spinach; spread mixture in bottom of prepared dish. Arrange squash over spinach mixture. Cover and chill the gratin up to 8 hours.

Preheat oven to 475 degree F. In a small bowl stir together the Parmesan and creme fraiche. Spread mixture over squash in dish. Bake, uncovered, for 15 minutes or until squash is tender and heated through and Parmesan mixture is lightly browned. Season to taste with salt and pepper, if desired. Makes 8 servings.

Variation

Homemade Creme Fraiche: If purchased creme fraiche is unavailable you can make your own. In a small mixing bowl stir together 1/4 cup whipping cream (not ultrapasteurized) and 1/4 cup dairy sour cream. Cover with plastic wrap. Let stand at room temperature for 2 to 5 hours or until mixture thickens. When thickened, cover and chill in the refrigerator until serving time or up to 48 hours. Stir before serving.